Recent analysis of ocean water samples across the Pacific point to Asian coal plants as the likely source of dramatic increases total mercury levels in the North Pacific Ocean over the last 20 years.  If present trends continue, the U.S. Geological Survey report  projects a doubling of oceanic mercury concentrations by the year 2050.  Oceanic mercury is converted to MethylMercury by algae, and then bioaccumulates up the food chain as algae is eaten by fish.  Fish harvested from the Pacific Ocean are a major contributor to human MethylMercury exposure, which is why scientists are focusing on the important health and ecological concern of the source of the oceanic mercury.  For more inforamtion see highlights on the USGS website.